1. Field of the Invention
This invention relates to a sheet material feeding apparatus for feeding sheet materials, a sheet material processing apparatus for effecting predetermined processing on sheet materials, and an image reading apparatus for reading the images of sheet-like originals.
2. Related Background Art
FIG. 19 of the accompanying drawings shows the construction of the essential portions of an image reading apparatus according to the prior art.
The reference numeral 1 designates an original supporting table, the reference numeral 2 denotes a driving motor for vertically driving the original supporting table, and the reference numeral 3 designates detecting means for detecting that originals have been moved up to a predetermined position.
The reference numeral 4 denotes a sheet feeding roller for moving the originals to a separating and feeding position, and the reference numeral 205 designates a sheet feeding clutch for changing over the ON/OFF of the driving of the sheet feeding roller 4.
The reference numeral 6 denotes a feeding roller, and the reference numeral 7 designates a separating roller of a comb-tooth like shape and roller portions exist alternately. The reference numeral 208 denotes a feeding clutch for switching ON/OFF the driving of the feeding roller 6, and the reference numeral 209 designates a separating clutch for switching ON/OFF the driving of the separating roller 7.
The reference numeral 10 denotes a conveying motor which is the drive source of the entire apparatus.
The reference numeral 13 designates a sheet feeding sensor which detects that an original has been separated and conveyed. The reference numerals 14 and 15 denote original reading sensors which read the image information of the front and back surfaces of conveyed originals. The reference numeral 16 designates a sheet discharge sensor which detects that the original F has passed a conveyance path and has been discharged.
The reference numerals 20, 21, 22 and 23 denote original conveying rollers which convey and drive the original F.
The reference numeral 40 designates an upper guide plate, and the reference numeral 41 denotes a lower guide plate, and the original F is conveyed between these two guide plates.
The reference numeral 30 designates a sheet thickness adjusting knob which moves up and down the feeding roller 6 to thereby change the spacing of a separating and conveying portion.
The operations of these are as follows.
When a plurality of originals F are stucked on the original supporting table 1 and a reading start signal is outputted from input means, not shown, the original supporting table driving motor 2 is rotatively driven to move up the original supporting table 1.
The originals F on the original supporting table 1 are gradually moved up, and the original supporting table driving motor is driven until the originals F are detected by the original detecting sensor 3, and is stopped at a point of time whereat the originals have been detected by the original detecting sensor 3.
Next, when the sheet feeding clutch 205 becomes ON, the driving of the conveying motor 10 is transmitted to the sheet feeding roller 4 to thereby rotatively drive the sheet feeding roller 4, thus conveying the original F to a conveying and separating portion.
The feeding roller 6 and the separating roller 7 are generally controlled so as to start driving simultaneously with the sheet feeding roller 4, and separate and convey the original F fed from the sheet feeding portion by the sheet feeding roller 4.
The original F is separated at a sheet separating and feeding portion by the following operation.
The original F conveyed to the sheet separating and feeding portion by the sheet feeding roller 4 is driven in the feeding direction by the feeding roller 6 and at the same time, has a force in the opposite direction imparted thereto by the separating roller 7.
Thereby, even if as shown in FIG. 20, a plurality of originals are fed at a time to the separating and conveying portion, only the upper original F1 is fed forwardly and the lower original F2 is returned reversely by the separating roller 7, thus preventing the double feeding of the originals.
The adjustment of the spacing between the two rollers 6 and 7 is effected by the use of the sheet thickness adjusting knob 30.
When as shown in FIG. 21, the spacing between the rollers of the separating and conveying portion is narrow, the original F is pushed back in a direction opposite to the direction of conveyance by the separating roller 7 and is not fed. Also, when as shown in FIG. 22, the aforementioned spacing is wide, if the force the second original F2 receives from the separating roller 7 is less than the static frictional force between the original F and the original F2, the two originals are conveyed at a time, thus causing double feed.
Therefore, it is necessary to change the sheet thickness adjusting knob 30 in conformity with the kind of the original to be read.
The original F which has passed the separating and conveying portion is detected by the sheet feeding sensor 13, and by the signal thereof, the sheet feeding clutch 205 and the feeding clutch 208 are disengaged to thereby once stop the driving of the sheet feeding roller 4 and the feeding roller 6 so that the second and subsequent originals F2 may not be continuously fed.
The separating roller 7 continues to reversely drive while the sheet feeding sensor 13 is detecting the original F so that the second and subsequent originals F2 may not be fed by being dragged by the original F1.
Via this process of separation and conveyance, the original F passes the reading sensors 14 and 15 and the read image thereof is sent to an image processing portion, not shown.
When a plurality of originals are to be continuously processed, the sheet feeding clutch 205 and the feeding clutch 208 are again engaged at a point of time whereat the sheet feeding sensor 13 has come not to detect the original F, and the sheet feeding roller 4 and the feeding roller 6 are driven to thereby begin to separate and convey the original F2.
At a point of time whereat the original detecting sensor 2 has come to detect no original even if the original supporting table 1 is moved up to its uppermost position, it is judged that all originals have been read and conveyed, and at a point of time whereat the discharging of the original F has been detected, the conveying motor 10 and the separating clutch 9 are deenergized, and then the original supporting table driving motor 2 is reversely rotated to thereby move the original supporting table 1 to its lowermost position, whereafter all operations are completed.
In the aforedescribed original conveying method according to the prior art, the sheet feeding roller, the feeding roller and the separating roller are controlled by the ON/OFF of the clutches, and the driving force is supplied from the conveying motor 10 through the gears, the belt, etc. and all the rollers are rotated at the same rotational proportion in any state.
Also, when the original reading speed and resolution are to be changed by changing the conveying speed of the conveying motor, the speeds of the sheet feeding roller, the feeding roller and the separating roller fluctuate at the same proportion, and the separating and conveying system which should originally be determined by the coefficient of dynamic friction between the originals and the coefficients of friction among the rollers also fluctuates and separation and conveyance are-effected in an unstable state, and this gives rise to a problem such as double feed.
Also, the operations of the rollers take place at a predetermined proportion through the gears and the belt and therefore, even if the state, quality, etc. of the originals changed, it is difficult to change and optimize the separating and conveying system, and it is also a cause of double feed that an external factor cannot be coped with.
In the construction as well, a number of gears and belts for deceleration and acceleration become necessary to adjust the rotational proportion of the rollers, and this makes the mechanical construction complicated and at the same time, leaves problems in maintenance property and stability. Regarding also the adjustment of the thickness of the sheets, only manual adjustment is possible and this is cumbersome, and when originals of different thicknesses are mixed, problems such as bad conveyance and double feed arise and remarkably aggravate the working property.